Glutamate is an important component of the taste of meat, cheese, and many other foods. It has long been known to be a chemostimulant for taste receptor cells, and elicits responses in a wide variety of animals including humans. This project outlines a series of experiments that will be part of a larger program studying the molecular physiology of glutamate receptors in mammalian taste buds. We begin with the premise that glutamate receptors in taste buds are similar to those that have been cloned and sequenced in the brain, namely, NMDA, AMPA, kainate, delta, and metabotropic glutamate receptor subfamilies. Our preliminary data indicate that a metabotropic glutamate receptor, mGluR4, similar to that in the brain is found in taste buds and that a novel ionotropic glutamate receptor, RdP2, is found in lingual tissue. The experiments in project #2 are aimed at localizing macromolecules associated with glutamate receptors in rat taste buds, namely mRNAs for glutamate receptors and proteins representing the membrane-bound receptors. We will utilize in situ hybridization to identify receptor mRNAs and immunocytochemistry at the light and electron microscopic levels to visualize receptor proteins. We will produce hybridization probes and antibodies based upon sequences identified in Project #1 (Chaudhari). We will generate synthetic peptides and fusion proteins to raise antibodies against glutamate receptors. Additionally, we propose to use conditioned taste aversion in rats to test the functional relevance of the glutamate receptors that are expressed in taste buds. The overall goal of this project, in summary, is to find where glutamate receptors are localized in taste buds and to explore whether they play a role in taste. These date will be correlated with information about the detailed molecular structure of glutamate receptors (Project #1, Chaudhari) and the biological function of glutamate receptors at the cellular level in taste buds (Project #3, Kinnamon).